flink@umcp-cs.UUCP (Paul V. Torek) (07/09/85)
In article <535@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: >So *most*, mutations are "harmful", this is where N[atural].S[election]. >comes in, it amplifies the few "beneficial" ones that do occur. Exactly. One creationist expressed bafflement at the idea that mutation could result in evolutionary chains that "go so far" as the "distance" between radically different organisms. But try this experiment: flip several (many) coins, and move to the right on a number line (start at zero) only when you get all coins coming up heads. This represents movement toward an adapted complex species. Move to the left every time you get any result other than all heads. Only there's one catch: you don't get to move to the left. You can go pretty far, with enough trials. --the evolving iconoclast, Paul V Torek
pmd@cbscc.UUCP (Paul Dubuc) (07/11/85)
A response to Paul Torek: >In article <535@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: >>So *most*, mutations are "harmful", this is where N[atural].S[election]. >>comes in, it amplifies the few "beneficial" ones that do occur. >Exactly. One creationist expressed bafflement at the idea that mutation >could result in evolutionary chains that "go so far" as the "distance" >between radically different organisms. But try this experiment: flip >several (many) coins, and move to the right on a number line (start >at zero) only when you get all coins coming up heads. This represents >movement toward an adapted complex species. Move to the left every >time you get any result other than all heads. Only there's one catch: >you don't get to move to the left. *How* do the beneficial mutations get amplified by Natural Selection? How does that "catch" in Paul's experiment relate to N.S.? Why don't some trials cause us to move to the left, or even cause us to start again from the beginning? Why must natural selection work the way Paul says it does? >You can go pretty far, with enough trials. Have there been enough yet? Why, of course, we've gotten pretty far haven't we? :-) -- Paul Dubuc cbscc!pmd
gordon@uw-june (Gordon Davisson) (07/12/85)
>>>[Stanley Friesen] >>>So *most*, mutations are "harmful", this is where N[atural].S[election]. >>>comes in, it amplifies the few "beneficial" ones that do occur. >>[Paul Torek] >>Exactly. One creationist expressed bafflement at the idea that mutation >>could result in evolutionary chains that "go so far" as the "distance" >>between radically different organisms. But try this experiment: flip >>several (many) coins, and move to the right on a number line (start >>at zero) only when you get all coins coming up heads. This represents >>movement toward an adapted complex species. Move to the left every >>time you get any result other than all heads. Only there's one catch: >>you don't get to move to the left. >[Paul Dubuc] >*How* do the beneficial mutations get amplified by Natural Selection? >How does that "catch" in Paul's experiment relate to N.S.? Why don't >some trials cause us to move to the left, or even cause us to start >again from the beginning? Why must natural selection work the way Paul >says it does? Harmful mutations have no lasting bad influence on a population because their carriars tend not to have many decendants. Thus, after a while, the mutation dissapears from the population. Beneficial mutations, on the other hand, cause their carriers to tend to have more decendants than the non-carriers, so after a while, most of the population carries the mutation, and the population has taken a step to the right (so to speak). -- Human: Gordon Davisson ARPA: gordon@uw-june.ARPA UUCP: {ihnp4,decvax,tektronix}!uw-beaver!uw-june!gordon
rlr@pyuxd.UUCP (Rich Rosen) (07/14/85)
> >You can go pretty far, with enough trials. [TOREK?] > Have there been enough yet? Why, of course, we've gotten pretty far > haven't we? :-) [DUBUC]1 A creationist WOULD put a smiley on the end of a perfectly good statement like that, wouldn't he? (Think about this Paul: we've come this far precisely because we've had enought trials; enough to come as far as we have. Maybe the subject line IS in error... -- Like aversion (HEY!), shocked for the very first time... Rich Rosen ihnp4!pyuxd!rlr
roy@phri.UUCP (Roy Smith) (07/15/85)
> *How* do the beneficial mutations get amplified by Natural Selection?
A perfectly reasonable question.
Let's suppose that due to a single nucleotide being wrong in my
DNA, the hemoglobin in my blood tends to crystalize when it shouldn't
(we're talking sickle cell anemia, here). I'm weaker, slower, etc. than
you are. I'm less likely to survive to puberty than you are because I
can't compete for food or run away from attackers as well as you can.
Even if I reach sexual maturity, I'm less likely to father children (and
pass on my mutated DNA to my progeny) than you are because when we fight
over a woman, you are likely to win. Thus, this random mutation gets
*selected against*.
I can't think of such a striking example in the other direction,
but the idea is the same. Suppose a random mutation causes my hearing to
be slightly better than yours in some way. I'm more likely to hear an
attacker in time to save myself than you are. When hunting, I'm better
able to tell where my prey is. In this case, the effect is small (as it
is with most beneficial mutations). However small the advantage is, I am
more likely to propagate my DNA than you are. This mutation gets
*selected for*.
Actually, the vast majority of mutations are harmful. This
doesn't change the basic idea, though. The harmful ones get weeded out
because they either don't survive or don't reproduce as well as the
wild-type (non-mutated) organisim.
When talking about mutations, one needs to make a differentiation
between phenotype and genotype. Phenotype refers to the observable
characteristics (the phenomena you can measure) of a system. Genotype
refers to the genetic makeup; the two are only loosely related. Small
changes in genotype can produce large changes in phenotype (as in sickle
cell anemia). Conversely, large changes in genotype can produce little or
no phenotypical changes.
Mutations are changes in the genotype. Evolutionary pressure is
applied, however, because of changes in phenotype. The single base change
mentioned earlier is a genotypical change. This genotypical change
produces the sickle cell phenotype. Which brings us back to what appears
to be a contradiction. If sickle cell anemia is bad for you, why *hasn't*
natural selection selected it right out of existence?
You have two sets of genes which make hemoglobin, one given to you
by your mother, the other by your father. The sickle cell phenotype is
recessive. That means that you only exhibit the symptoms if *both* of
your copies of the gene are defective. If only one copy has the sickle
cell genotype, you are said to the have sickle cell trait; you can pass it
on to your children but you don't have the symptoms yourself.
Well, it turns out that having sickle cell trait is actually
beneficial. If you have the trait, you make both the good and the bad
kinds of hemoglobin. It turns out that this is sufficient to make your
red blood cells function properly and you don't get sick. However, the
parasite that causes malaria lives in your red blood cells, and *it* can't
tolerate the mixture of good and bad hemoglobin.
So we have an interesting situation. People with sickle cell
trait have protection against an often fatal disease so the trait gets
selected *for*. On the other hand, two people with sickle cell trait have
a 25% change of their children having the anemia, so it gets selected
*against*. Which of these factors stronger? Check back with me in a few
million years and I'll let you know.
--
allegra!phri!roy (Roy Smith)
System Administrator, Public Health Research Institutelonetto@phri.UUCP (Michael Lonetto) (07/16/85)
> A response to Paul Torek: > > >In article <535@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: > >>So *most*, mutations are "harmful", this is where N[atural].S[election]. > >>comes in, it amplifies the few "beneficial" ones that do occur. Miller replies: > *How* do the beneficial mutations get amplified by Natural Selection? > How does that "catch" in Paul's experiment relate to N.S.? Why don't > some trials cause us to move to the left, or even cause us to start > again from the beginning? Why must natural selection work the way Paul > says it does? > SIMPLE ANSWER: THE HARMFUL MUTATIONS CAUSE DEATH. please people, I'm getting ready to give up on you. -- ____________________ Michael Lonetto Public Health Research Institute, 455 1st Ave, NY, NY 10016 (allegra!phri!lonetto) "BUY ART, NOT COCAINE"
dubois@uwmacc.UUCP (Paul DuBois) (07/17/85)
>>>You can go pretty far, with enough trials. [TOREK?] > >> Have there been enough yet? Why, of course, we've gotten pretty far >> haven't we? :-) [DUBUC]1 > > [Rosen] > A creationist WOULD put a smiley on the end of a perfectly good statement > like that, wouldn't he? (Think about this Paul: we've come this > far precisely because we've had enought trials; enough to come as far > as we have. Can you say "beg the question"? Good, I knew you could. Hence, the smiley. -- | Paul DuBois {allegra,ihnp4,seismo}!uwvax!uwmacc!dubois --+-- | "More agonizing, less organizing." |
rlr@pyuxd.UUCP (Rich Rosen) (07/19/85)
>>>>You can go pretty far, with enough trials. [TOREK?] >>> Have there been enough yet? Why, of course, we've gotten pretty far >>> haven't we? :-) [DUBUC]1 >> A creationist WOULD put a smiley on the end of a perfectly good statement >> like that, wouldn't he? (Think about this Paul: we've come this >> far precisely because we've had enought trials; enough to come as far >> as we have. [ROSEN] > Can you say "beg the question"? Good, I knew you could. > Hence, the smiley. [DUBOIS] When you ask a question that begs it own answer, phrased in such a way as to offer only its own assumed answer. It's really very simple. In this universe, with these physical laws, over this past n periods of time, so much has happened, enough to (wow!) get us where we are today. To ask "why" this happened is to ASSUME that someONE or someTHING deliberately caused it all to happen. "[Hawking thinks that] the only way to explain our universe is by our presence in it. This principle can be paraphrased as 'Things are as they are because we are.' According to one version, there is a large number of different and separate universes. Each has different values for its physical parameters and for its initial conditions. Most will not have the right conditions for the development of intelligent life. However, in a small number there will be conditioned and parameters as in our universe. In those it will be possible for intelligent life to develop and ask the question 'Why is the universe as we observe it?' The only answer will be that if it were otherwise, there would be nobody to ask the question." ---Stephen Hawking as quoted in "Stephen Hawking's Universe" by John Boslough Now, who's begging what? (I sometimes wonder if creationists could ever think of the universe in this way. So simple a child could understand it, but a creationist, well..... :-? ) -- "Wait a minute. '*WE*' decided??? *MY* best interests????" Rich Rosen ihnp4!pyuxd!rlr
dubois@uwmacc.UUCP (Paul DuBois) (07/19/85)
>> A response to Paul Torek: >>>In article <535@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: >>>>So *most*, mutations are "harmful", this is where N[atural].S[election]. >>>>comes in, it amplifies the few "beneficial" ones that do occur. > Miller replies: >> *How* do the beneficial mutations get amplified by Natural Selection? >> How does that "catch" in Paul's experiment relate to N.S.? Why don't >> some trials cause us to move to the left, or even cause us to start >> again from the beginning? Why must natural selection work the way Paul >> says it does? > [Michael Lonetto] > SIMPLE ANSWER: THE HARMFUL MUTATIONS CAUSE DEATH. Simplistic, you mean. Harmful mutations do *not* always cause death. So what about the ones carried along in the population, the extent of which is, evidently, inversely related to the degree of harmfulness? > please people, I'm getting ready to give up on you. That's unfortunate. Perhaps your impatience caused you to fail to notice that the question was about beneficial mutations, not harmful ones. You answered (poorly) a different question. -- | Paul DuBois {allegra,ihnp4,seismo}!uwvax!uwmacc!dubois --+-- | "More agonizing, less organizing." |
fritz@phri.UUCP (Dave Fritzinger) (07/24/85)
> >>>In article <535@psivax.UUCP> friesen@psivax.UUCP (Stanley Friesen) writes: > >>>>So *most*, mutations are "harmful", this is where N[atural].S[election]. > >>>>comes in, it amplifies the few "beneficial" ones that do occur. > > Miller replies: > >> *How* do the beneficial mutations get amplified by Natural Selection? > >> How does that "catch" in Paul's experiment relate to N.S.? Why don't > >> some trials cause us to move to the left, or even cause us to start > >> again from the beginning? Why must natural selection work the way Paul > >> says it does? > > > [Michael Lonetto] > > SIMPLE ANSWER: THE HARMFUL MUTATIONS CAUSE DEATH. > > Simplistic, you mean. Harmful mutations do *not* always cause death. > So what about the ones carried along in the population, the extent of > which is, evidently, inversely related to the degree of harmfulness? > > > please people, I'm getting ready to give up on you. > > That's unfortunate. Perhaps your impatience caused you to fail to > notice that the question was about beneficial mutations, not harmful > ones. You answered (poorly) a different question. > Paul DuBois {allegra,ihnp4,seismo}!uwvax!uwmacc!dubois --+-- Okay, let's try another SIMPLE answer. THOSE MEMBERS OF A SPECIES WITH BENEFICIAL MUTATIONS SURVIVE BETTER, AND BREED BETTER. (After all, they are beneficial mutations). It is in this way that beneficial mutations are selected for by NS. This answer does seem obvious!!! I too am getting ready to give up on you!!! Dave Fritzinger PHRI, NY,NY allegra!phri!fritz
rlr@pyuxd.UUCP (Rich Rosen) (07/26/85)
> Okay, let's try another SIMPLE answer. THOSE MEMBERS OF A SPECIES WITH > BENEFICIAL MUTATIONS SURVIVE BETTER, AND BREED BETTER. (After all, they > are beneficial mutations). It is in this way that beneficial mutations > are selected for by NS. This answer does seem obvious!!! > [Dave Fritzinger replying to Paul Dubois] No, No, No!!!! Never state the OBVIOUS to Paul Dubois!! He'll just come back with the ultimate retort: "PRO-FOUND!!!!!" Better to say that, perhaps, than to answer the questions that such obvious notions obviously pose for his doctrine. -- Anything's possible, but only a few things actually happen. Rich Rosen pyuxd!rlr